Sony VaioPCG-8A2P

Hey!
I've also got one of those machines, yet this one boots none. It doesn't even power on the display, yet, the HDD works and so. What can it be?
I'll try to replug everything back tomorrow, and check it out, but, if does nothing (Not even the backlight) what can it be?

1- Any LED flashing / blinking?
2- The HDD is spinning or is it also trying to read anything ?
3- Is the display completely OFF or turns on for 1 second or less?
4- Any "beep" signal when you turn on the PC ?

Try also to connect an external monitor to VGA out and see what happens.